Certain climatic conditions, particularly those characterized by cool, humid weather, may cause the formation of icy deposits on the internal portions of a carburetor which have been chilled by the evaporation of the volatile fuel, and entrained water vapor. The formation of ice within the carburetor venturi, on the fuel jets, and on the throttling mechanism, is particularly hazardous in the case of internal combustion aircraft engines. Heretofore it has been a common practice to divert air heated by the engine's cooling or exhaust systems into the carburetor to prevent icing. This has not been altogether satisfactory for a number of well-known reasons, and imposes significant engine performance penalties. Among the drawbacks of heated-air de-icer systems are the undesirable expansion and evaporation of the fuel, and the lowering of the density of the air/fuel mixture.
To overcome these aforementioned shortcomings of heated-air de-icers, various means have been proposed heretofore to provide improved de-icer systems. Typical of these schemes are the use of electrical heating elements, as disclosed in U.S. Pat. No. 3,128,321 to Hammerschmidt, and U.S. Pat. No. 2,941,061 to Bowers. Other means for suppressing carburetor ice formation, or the adverse effects thereof, are based upon novel geometry of the carburetor mechanism such as that disclosed in U.S. Pat. No. 2,693,175 to Hickok et al, and U.S. Pat. No. 3,057,609 to Hegna.
It has been proposed to obviate the undesired effects of directly heating the air portion of the air/fuel mixture entering the carburetor by heating the body structure of the carburetor in the manner disclosed in U.S. Pat. No. 2,719,519. Although this represents an improvement over many of the prior approaches to solving the icing problem, it has its own drawbacks including an adverse effect on engine idling performance. For this reason, the device disclosed in U.S. Pat. No. 3,916,859 was invented by the inventor of the present application, which in turn is an improvement thereof.
While not directed to the problem of carburetor icing, the following U.S. Pat. Nos. are illustrative of prior art, inventions which have as their objective the use of engine heat, conducted via either exhaust air or lubricating oil to assist in the vaporization of fuel entering the carburetor; 1,078,919 to Hall; 3,016,890 to Bibo; 3,150,652 to Hallabaugh; and 3,459,162 to Burwinkle et al.